In which animal sweat is of red colour

Correct Answer: D

Rationale: The correct answer is D: Shrew. Shrews are known to have red-colored sweat due to a pigment called porphyrin. This pigment gives their sweat a reddish hue. Kangaroos, elephants, and rhinoceroses do not have red sweat. Kangaroos sweat is colorless, elephants' sweat is clear, and rhinoceroses sweat may appear red due to mud or dust, not because of any pigment. Therefore, the red-colored sweat is unique to shrews, making choice D the correct answer.

Correct Answer: B

Rationale: The correct answer is B: Elasticity of dermis decreases. As people age, the dermis layer of the skin loses collagen and elastin fibers, leading to a decrease in skin elasticity, resulting in loose and wrinkled skin. The other choices are incorrect because A (Stratum germinativum becoming more active) would actually lead to increased cell turnover and potentially smoother skin, C (Stratum corneum becoming thicker) would result in thicker skin but not necessarily loose and wrinkled, and D (poor blood supply to the skin) would affect overall skin health but not directly cause loose and wrinkled skin.

Correct Answer: B

Rationale: The correct answer is B: Involuntary. Muscles found in the skin, such as arrector pili muscles responsible for hair erection, are involuntary muscles. These muscles respond to autonomic nervous system signals without conscious control. Choice A is incorrect because muscles in the skin are not under voluntary control. Choice C is incorrect because it suggests a combination of voluntary and involuntary muscles, which is not accurate for skin muscles. Choice D is incorrect as there are indeed involuntary muscles in the skin.

Correct Answer: A

Rationale: The correct answer is A. When exposed to sunlight, the skin responds by widening the capillaries to allow more blood flow, leading to a reddish appearance. This process is known as vasodilation. Option B is incorrect as blood cells do not ooze out through skin pores. Option C is inaccurate as haemoglobin breakdown does not cause skin reddening. Option D is also incorrect since the spleen does not release more blood in response to sunlight.

Correct Answer: D

Rationale: The correct answer is D: Cold. Dense fur in cold temperature animals acts as insulation to retain body heat and protect them from the cold. The fur traps air close to the body, creating a layer of warmth. This helps regulate their body temperature and prevent heat loss. Snow (A) is not the main threat as the fur insulates against it. Air (B) is actually trapped by the fur to provide insulation. Enemies (C) are not directly protected against by dense fur, as it primarily serves to regulate body temperature in cold environments.